iStock/Thinkstock(RIVERHEAD, N.Y.) -- An accused rapist used paper airplanes in an attempt to orchestrate a jailhouse plot to kill his alleged victim and a witness and mail the witness' head to his family, according to authorities in Suffolk County, N.Y.

Patrick O'Sullivan, 21, sent "kites," or paper-airplane notes that inmates use to pass messages, to another inmate who he wanted to commit the killing, Suffolk County District Attorney Thomas Spota said at a news conference announcing new charges against the man.

O'Sullivan was charged in December with raping a female in Suffolk County and is being held in Riverhead Correctional Facility, in Riverhead, on Long Island.

From around the end of June through September, O'Sullivan allegedly passed the names of his alleged victim and a witness in the case against him, as well as instructions and his victim's address, to the other inmate, the district attorney said. O'Sullivan even drew a map of the home of the alleged victim and witness, Spota said.

O'Sullivan allegedly told his fellow inmate to throw the victim's body in the water so it would not be found, but asked that the witness' body be buried in a certain place so that once O'Sullivan got out of jail, he could dig up the head and send it to the witness's family, Suffolk County authorities said at the news conference.

"As long as you get that done" -- kill the rape victim -- "ishould [sic] be Gucci," he wrote, according to the district attorney's office. "Gucci" is a prison slang term for "good" or "OK," police said.

"Once you do it I consider myself in debt to you," O'Sullivan wrote, the district attorney's office said.

But O'Sullivan's alleged plot fell apart when the other inmate told police about the notes the two passed back and forth. That inmate was released early in exchange for his help; authorities did not release his name.

O'Sullivan was charged with two counts of conspiracy in the second degree for the alleged plot, according to the district attorney's office.

In connection with the alleged rape, O'Sullivan had been charged with four counts of predatory sexual assault, rape in the first degree, criminal sexual act in the first degree, two counts of criminal use of a firearm, burglary in the first degree and sexual abuse in the first degree.

He has been in the county jail since Dec. 1 in lieu of $100,000 cash bail or $1 million bond, Spota's office said.

With the new charge, Spota said in a statement Wednesday, "upon conviction, he will be in prison for decades."

O'Sullivan's attorney, William Keahon of Hauppauge, N.Y., did not respond to a request for comment Friday afternoon.